Re-ordered movegroup's initialization, so capabilities start after monitors.

This is intended to fix #378.

Capabilities starting after monitors means that a client which waits on a capability to become ready (via SimpleActionClient::waitForServer() for instance) can be sure that the rest of move_group is already initialized and thus ready to be used.

In a long-running system this is not really an issue, but for tests which start up a new instance of move_group each time, this is a big problem.

I don't know much about the other capabilities for move_group, so I don't know if this will cause trouble for them.  I do know it makes my own particular capability and its client work nicely though.